Apparatus for melting brass chip scrap



1965 o. A. HUHTALA ETAL. 3,2Q2 2fi APPARATUS FOR MELTING BRASS CHIPSCRAP Filed Sept. 23, 1960 4 Sheets-Sheet l 3-; IN V EN TOR-5 010w 0.Huh 7:44, m ROBERT L. JiUC/(US 5;; BY fa flair ATTORNEYS Aug. 1 5 o. A.HUHTALA ETAL smzms APPARATUS FOR MELTING BRASS CHIP SCRAP Filed Sept.23, 1960 4 Sheets-Sheet 2 INVENTORS 0144/10 J9, HuHmw ADOBE/97' L.JI'OC'KUS M W 1965 o. A. HUHTALA ETAL 3,202,408

APPARATUS FOR MELTING BRASS CHIP SCRAP Filed Sept. 25, 1960 4Sheets-Sheet 3 O O O INVENTORS 01.0w 6 HUHTALIJ By ROBERT L STOCA US hemATTORNEYS Aug. 24, 1965 O. A. HUHTALA ETAL APPARATUS FOR MELTING BRASSCHIP SCRAP Filed Sept. 25, 1960 4 Sheets-Sheet 4 01 V/ I H P0 5597 L.STOCKUS ,JQOMW Am Arron 139 United States Patent 3,2tt2aitt3 APPARATUSMELTHJG BRASS @Hll g-CRAP Giavi A. Huhtala, 'Ncwtcwn, and Robert L.Stockus,

Grange, 2min, assignors to Chase Brass Copper (30.,

incorporated, Waterbury, onn., a corporation of Connecticut Filed ept.23, 1969, Ser. No. 58,057 6 @lairns. (Cl. 266- 33) The present inventionrelates to conversion of scrap metal of small particles size by meltingand casting the scrap into pigs, ingots or billet in order to recoverthe metal in a form that can be used practically. More particularly, theinvention is concerned with apparatus for converting to usable billetform large quantities of fine brass chips, shavings, turnings, boringsand similar small particle scrap resulting from ordinary machiningoperatlons. The invention is of most immediate importance in theconversion of free-cutting brass chip scrap of which there is normally avery large amount available but which in the past has not been readilyutilizable.

As used herein, the form chips is employed to designate the smaller,lighter scrap metal particles resulting from machining metal stock,rather than the heavier type of scrap comprising chunks of rod, bar,tube, pieces of castings or other fabricated metal shapes. Generallyspeaking, this heavier scrap can be remelted in a furnace without toomuch difliculty because the individual pieces of scrap have substantialweight for their size, that is their specific surface-to-weight ratio isrelatively low. This is not true of the fine chips with which thisinvention is more especially concerned Where the surface-toweight ratio,both of the indivdual particles and of the aggregate formed thereof, isof a much higher order. This lighter form of chip is composed ofparticles of nonuniform, highly random individual sizes and shapes, butprevailingly is characterized by being relatively thin and long inproportion to thickness and in having a tendency to curl. Perhaps thismajority of the particles can best be described as curved platelets ofup to about 0.0K) inch thickness and from one-quarter to one-half inchin length along a maximum dimension, although a minor proportion ofalmost dustlike lines and another of long, stringy slivers are alsopresent. This type of chip in the aggregate is extremely diilicult tomelt in a furnace, as will be discussed in more detail presently. Thisdifficulty is so well recognized in industry that care is taken toseparate it from the heavier, chunkier type of scrap. In fact it sellsat a substantially lower price than does the heavier scrap for this veryreason.

The invention here disclosed makes it possible to charge scrap meltingfurnaces with 100% chip scrap which has heretofore not been practical oreconomical in spite of numerou attempts. The invention, althoughconcerned more especially with the handling of chip scrap, providescertain advantages in reclaiming heavier scrap also, either by itself orin admixture with chip scrap, and this is accordingly not excluded.

The practical recovery in usable form of line metal chips is an oldproblem of long standing in the art, and a great many proposals forsolving it have been advanced over the years. it has long beenrecognized that the difiiculty is due largely to three factors:

(1) The surface oxidation of the chips, particularly under the elevatedtemperatures and in the presence of air, water vapor, etc, obtaining inthe zone in which the chips are introduced into the furnace, inhibitsready acceptance of the chips into the molten mass and in additionproduces excessive dross;

(2) The light Weight of the particles further tends to greases ?atentedAug. 24, 1965 cause them to float on or mix with the drossy layer on thesurface of a melt rather than sink into and be absorbed by the melt, and

(3) In the conventional melting, chips are not fed at a. continuous,steady rate conforming to the rate at which they can be melted by theenergy input of the furnace. Instead, they are usually added all at onceat the start of a heat or at least in relatively large increments withthe result that they heat up over a protracted period of time and in astrongly oxidizing atmosphere. Even when they attain or definitelyexceed the melting temperature, a substantial portion of them simplyball up or spheroidize with an intact oxide coating which effectivelyprevents wetting by and assimilation into the bath. The net result is avery large loss in the form of skimmings which are usually removed aftereach heat.

The rapid and extensive oxidation of the chips when attempt is made tointroduce them into a melting furnace in the Way heavier chunk scrap isordinarily fed of course leads to the formation of a high percentage ofdross or slag, with concomitant loss of metal values in reclaiming thescrap. Such losses commonly run from 5% to 8% of the metal introducedWhere chip charges to the furnace have been tried in the past. Becauseof the very large tonnage of chip scrap available for conversion, lossesof this order become a highly significant factor since they mayrepresent several tens of thousands of dollars annully in a largecasting shop;

In an earlier Patent No. 2,446,637 there is disclosed a method ofconverting brass chips involving the use of an enclosed melting furnaceand the supply thereto of a reducing gas mixture to maintain anonoxidizing atmosphere through which the chip scrap is dropped into themelt. While this method has been used, the necessity for enclosing thefurnace and supplying a special reducing gas thereto has practicalcommercial disadvantages.

It has also been common practice in the past to attempt to reduceoxidation losses by mixing a smaller portion of chip scrap with asubstantially larger portion of heavier chunk scrap, and this method isprobably still used predominantly in casting shops today where largequantities of chips are melted. The large chunk scrap in this system,together with manual stirring of the melt in the furnace, is relied uponto carry the fines into the melt and this does occur to a limiteddegree. This permits some utilization of the fine scrap but metal lossesare not significantly reduced and the method is subiect to the definitelimitation that the amount of fine scrap that can be utilizedis'restricted by the availability of the heavier chunk scrap.

Another scheme that has been proposed is that of briquetting orcampacting into block form by heavy pressure quantities of fine chipscrap and then introducing the briquett-e into the furnace. Experiencewith this, however, has shown that while this is an aid in the handlingor introducing of the chips into the furnace, it does not materiallyimprove the situation in respect to getting rapid melting. In practice,increasing difliculty of melting the briquettes with succeeding chargesin a furnace is encountered, requiring more rabbling or puddling by thecaster. There is a concomitant increase in slag on the melt requiringmore frequent skimmings and resulting in lower metal recovery with eachsucceeding round. Also unless the briquettes are made at extraordinarilyhigh pressures and thus have unusually high density, they are prone todisintegrate during heating, thus in effect reverting to loose chipswith attendant poor melting per-formancc.

It will be appreciated also that this fine scrap is usually saturatedwith cutting oil which adheres to the chips, even in the briquettedform, and the vaporization of the oil when the chips or briquettes areintroduced into the furnace produces such volumes of smoke and flamethat it I soon becomes quite unbearable for the operator or caster.

least necessary to pay bonus rates to getworkmen to accept such a job.Schemes have been devised formech-anically actuating a rabbleforeffecting this pushing or puddling, and other devices proposed tomechanize the skimming operations, so that a caster is relieved to someextent from-exposure to the intense heatand large volumes of soot andsmoke. So far,'however, these prior schemes have been only moderatelysuccessful under 'the most favorable conditions, and thesedo notordinarily'obtain in practice. i

There are other disadvantageous 'side effects encountered in the priorpractice of handling fine metal chips, such as widely variable energyinput to the melting furnace resulting. in lower over-all operatingefiiciencyf Furthermore, cluev to the oxidizing conditions and to thewide variation in molten meta-l level arising from tilting a fur pace topour off the molten metal, which has been the usual practice, slagincrustations are caused to build up on the sidewall of the crucible,reducing its holding capacity and necessitating that the furnace thetilted farther over in order to pour a full mold. In normal use,portions of these incrustationsoften break loose and work down into theinductor channels of the furnace, causing them to clog and overheat. Inorder to keep the furnace in good condition, it is necessary andcustomary to chip or clean off these incrustations and to ram thechannels about once a day. This is a hot, dirty, time-consuming job.'

In a copending application Ser. No. 58,056 filed'concurrently herewithnew. Patent No. 3,123,466 issued March 3, 1964, there, is described anovel method of melting large volumes of fine chip metal scrap on anindustrial scale for the economic recovery of the metal content incommercially usable'form. Reference is made to that application for afuller description of the method involved butit will be helpful to abetter understanding of this invention to give the following briefdescription of the method'inv'olved. As disclosed in theaforesaidcope'nding application, the method comprises introducing fine metalchips into a furnace at a controlled rate of feed approximately equal tothe instantaneous capacity of the furnace-to absorb the incoming chips.A melt is maintained in the furnace and a thick protective fluid-likemedium of finely divided carbonaceous material isprovided on its surfaceto produce a strongly reducing atmosphere blanketing the' rnelt andextending above it sufficiently to enable incoming chips to beintroduced therein below their oxidation temperature. The chips uponbeing fed into the furnace, fall onto the carbonaceous blanket and areassisted by mechanical stirring or rabbling to effect intimate contactwith the carbonaceous medium of the blanket in order to preventoxidation of the chips while they are heated to their meltingtemperature and become absorbed in the mass of molten metal in thefurnace. The above-described method further includes the step ofsimultaneously withdrawing the molten metal from the furnace at a ratesuch that the level of the furnace remains virtuallyconstant. i f I Itis the main objective of the invention disclosed herein toprovideapparatus particularlysuitable for practicing the method justdescribed. The apparatus herein after'describedachieves a numberofimportant correlated objectives in the art of melting chip scrap,which include better control of the feed of the chip scrap to the-melting furnace, elimination of undesirable portions of or inclusionsin the scrap, simplification of equipment and reduction of maintenance,and the automation of such equipment to reduce or eliminate variationsarising from inaccuracy of manual control. These and other objectstransferring the chips to a melting furnace, agitating or pusher meanscooperating with the melt furnace to assist in getting the chips intothe body of molten metal in the furnace crucible, an auxiliary holdingor pouring furnace, billet molds and miscellaneous equipment forcoordinating the over-all operation;

FIG. 2 is a view in plan of the installation shown in FIG. 1;

FIG. 3 is a cross-sectional view through the melt furnace showing thecarbonaceous blanket on the surface of the molten metal, the pusherhead, in greater detail and arrangements for effecting underpouring ofthe metal and for mounting a temperature sensitive element in the bodyof the melt; l

FIG. 4 is a view, partly in section, through the holding furnace showingthe tilting arrangement therefor;

FIG. 5 is a plan view, taken on line 5-5 of FIG. 3, of an arrangementfor effecting distribution of the chips across the projected surface ofthe metal in. the melt furnace;

FIG. 6 is a fragmentary view of a portion of the conveyor system used tomove chips from the storage bin toward the melt furnace;

FIG. 8 is a sectional view in end elevation on line 88 of FIG. 1 showingportions of the chip bin and feed mechanism.

It will be helpful first to consider in outline the several operationalsteps involved in carrying out the method as it pertains to the formofapparatus shown in the drawingsJ Referring to these drawings, and moreparticularly to FIGS. 1 and 2 thereof, fine brass chips C are dumpedinto a bin 20 from which they feed by gravity through a hopper 22 onto aconveyor 24. The latter transfers the chips to a generally circular binor bowl 26 forming part of a vertical conveyor 28. Projecting axiallyupward from the center of bowl 26 is a helical conveyor flight 27 whichcarries the chips upwardly from the-bowl and discharges them into thehopper of amagnetic separator 30, the drive unit for which is indicatedat 32. After passing through the separator, the chips are delivered ontoa generally horizontal conveyor 34 by which they are then introducedinto the crucible 37 of a melting furnace 36. Conveyor 34 has a forwardextension 38 overlaying the open upper surface of the furnace, whichextension helps to distribute the chips uniformly across that .surface.A mechanically actuated rabble or pusher 40, positioned centrally abovethe open crucible, is supported by a gooseneck arrangement comprising ashaft or column 42 depending from an overhead cantilever beam 44 formingpart of apparatus 46 located beneath the furnace for reciprocatingpusher 4t} verticallytoward and away from the surface of the moltenmetal in the crucible; Conveyor extension 38 is specially contouredto'allowshaft '42 of pusher head 40 to extend downwardly, axially of thecrucible of furnace 36. The pusher apparatus '46 is arranged not only toimpart vertical reciprocation to pusher head 40 but also to rotate thehead 'in a horizontal plane within'angular limits as shown in dottedlines in FIG. 2. It is not'desired that the pusher 40 come into actualcontact withthe molten metal itself, and its lower. limit ofreciprocation is accordingly adjusted to prevent this. At its uppermostposition, pusher 40 is raised sufficiently above the surface of the meltin'the crucible to allow incoming chips to be distributed evenly acrossthe entire exposed surface of the crucible.

The upper surface of the furnace crucible is completely covered by athick blanket B (see FIG. 3) composed of granular carbon particles ofsmall diameter. In present commercial practice, blanket B is maintainedat a minimum thickness of about 4 inches, and 6 inches or more ispreferable, to provide at the surface of the molten metal a zone offluid-like medium which is highly reducing in nature. The chips are thusintroduced into a protective medium on the surface of the molten metalin the furnace in such manner that they are received below theiroxidation temperature and are heated by intimate contact with thefluid-like medium under conditions which prevent oxidation while beingraised through such contact to their melting temperature. Thecomposition of this blanket of carbon granules is such that, underoperating conditions, it is very fluid, offering minimum resistance tothe passage therethrough of the fine metal chips While at the same timeeffectively excluding access of air both to the upper surface of themelt in the furnace and to the chips themselves in the zone directlyabove the furnace where they are subjected to the intense heat of themolten metal immediately prior to coming into contact therewith. Furnaceso is equipped with an underpour overflow feed spout 558 which serves todraw off molten metal from below the surface thereof iii the crucibleand maintains the level of the melt in the furnace substantiallyconstant. This molten metal by more or less continuous overflow throughspout So without tilting of melt furnace 36 is delivered by a launder S2to a second furnace 5d, hereinafter termed the hold or pour furnace,which is substantially similar to crucible furnace 3-6. In this case,however, furnace 51% is mounted on trunnions sa whose axis passessubstantially through the lip 58 of the pour furnace, whereby tilting ofthe furnace causes metal to flow over the lip into a strainer or tundishas having a chute to deliver the molten metal to the cavity of a billetmold as. The billets (Pi 1), when cooled, are removed from mold 62 andare lowered by a hoist 63 onto a conveyor (id for delivery to skids 6%for temporary storage.

In operating the system, optimum results are obtained by careful controlof the rate of feed of the chips to melt furnace 36, so that theinstantaneous rate of delivery of the chips to the furnace is held asclosely equal to the instantaneous capacity of the furnace to melt thechips as is practical to achieve. This capacity of the furnac isdetermined from moment to moment by the temperature of the molten metalin the melting furnace crucible, and the furnace is equipped with athermocouple installed in a tube 65 for determining this. The electricalsignal produced by this thermocouple is fed to a conventionalproportional electronic control device 7%) which in turn controls thedrive unit 29 for spiral conveyor 28, whereby the rate of feed of thechips to the furnace is continuously regulated in accordance with thetemperature of the molten metal in the furnace.

With the foregoing perspective in mind of the general steps involved infeeding and melting the chips, a further detailed description of theparticular apparatus here illustrated for accomplishing the steps willnow be given.

Referring to FIGS. 1, 2 and 8 of the drawings, the brass chips C flowdownwardly from bin 2t to an open hopper 22 where they are depositedonto chute 72 form ing the load carrying member of conveyor Transport ofthe chips along chute 72 is effected by oscillating or vibrating thechute rapidly through a cycle comprising limited forward and upwardmovement and return, whereby forward momentum is imparted to the chipson the chute. Resilient mounting means 73 for the chute permits itsoscillatory motion in this manner. There is a certain range offrequencies or speed of vibration in which substantial synchronism withthe natural period of vibration of the chips is achieved, whereby byvarying 6 the frequency of vibration of the chute within this range, therate of progress of the chips along the chute can be accuratelycontrolled. Motive means (not shown) are provided for producing thisvibration and controlling its frequency. Apparatus of this type is Wellknown, and is available commercially.

Chips C are thus transferred from hopper Eli and delivered to thehelical conveyor feed bowl 26. Here the chips are deposited onto agrizzly 7d of roughly U-shaped configuration (see FlG. 2) consisting ofclosely spaced parallel bars forming a rough grate through which thefine chips are free to fall while long curled chips, commonly referredto as hay, are temporarily retained. Separation of the hay is desired asthis tends to clog the even flow of chips to the furnace, and this typeof scrap, because of its greater w ight, does not present as difficult amelting problem as the fire chips and can therefore be separatelyintroduced into a furnace in conventional manner with little difficulty.Grizzly 74 is mounted directly on bowl as, and both the bowl and thehelical flights 27 of conveyor are mounted for gyratory reciprocationwhereby both are angularly reciprocated back and forth about the axis ofthe helix is short rapid strokes which also have a vertical component.By reason of the mounting of grizzly 74- integrally on bowl 2-6, thegrizzly is also rapidly oscillated and causes any accumulated hay andoversize scrap to progress along the course of the grizzly, incounterclockwise direction as viewed in FIG. 2, to be finally dischargedinto a portable bin or collection cart 7.7.

Feed of chips C from bin to the spiral conveyor bowl 126 is controlledautomatically by the level of the chips in the bowl. For this purpose,the bowl is provided with two sets of insulated electrodes spaced aboutits circumference and defining a high level and a low level conditionfor the supply of chips maintained in the bowl. Referring to FIG. 6,electrodes 166, 163 each constitute one of a number of similar suchelectrodes in the lower and upper sets, respectively. Although notshown, a plurality of these electrodes are connected in parallel Withineach set as a precaution against malfunctioning of any one or" them. Therespective electrodes are mounted in insulating blocks 167 which aresecured in apertures provided for that purpose in the wall of the chipbowl 2.6 so as to expose the inner ends of the electrodes to contact bychips present in the bowl. When there are chips in the bowl at the levelof any electrode, a grounding circuit is completed from that electrodeto the bowl through the chips themselves. A relay control (not shown)mounted adjacent the drive unit for conveyor 24 under bin 26 isconnected by suitable conductors to the respective sets of lower andupper electrodes res, 16%, whereby conveyor 24 is caused to operatewhenever the level of chips in bowl as drops below electrodes res and tocontinue until the level reaches the upper electrodes 168, at which timethe circuit is broken and remains broken until the level again fallsbelow that of the lower electrodes.

Helical conveyor 2-8 operates on substantially the same principle asconveyor 24 in that the frequency of the stroke and the pitch of thehelices of flights 27 are so coordinated that the chips tend to g'umpforwardly and upwardly from bowl as along the helical path defined bythe flights 27, finally arriving at discharge point 36 at the upper endof the conveyor. The delivery of chips from bowl to the upper dischargepoint can thus be regulated by the speed of oscillation or vibration ofcon veyor at A variable speed drive unit 32 (see FIGS. 2 and 6) effectsthis, and the speed of this drive unit is made responsive toproportional control device 76.

Upon delivery of the chips to the magnetic separator 32, iron and othermagnetic inclusions are picked up on a magnetic drum (not shown) andcarried to a discharge point where they are removed and pass downthrough a chute 84 for delivery to a scrap cart or other suitablecollection device.

surface 86 as the latter vibrates.

furnace 36. Apron 38 is provided with longitudinal slats or ribs 39, andis countoured at its outer free end to effect uniform distribution ofthe chips. From the apron, the chips drop into blanket B of carbonaceousparticles and are enveloped by it, being able to sink rapidly into it byreason of its highly fluid nature. The optimum initial partcle size ofthe blanket material is important and is desirably less than that of thechips themselves, being on the order of one thirty-second of an inch indiameter.

The apparent specific gravity of the carbonaceous material in blanket Bunder the conditions existing in the furnace is desirably somewhat lessthan that of the chips, to facilitate the sinking of the chipstherethrough. A carbonaceous material meeting these requirements isavailable commercially under the trade name Micronex which is a type ofchannel carbon black marketed in dustfree bead form by Binney & SmithCo., New York, NY. Statex-R, manufactured by Southern Carbon Co.,Monroe, La. is another suitable material.

As some of the carbon is of course consumed in'the furnace, it must bereplaced to maintain the desired thickness of the blanket. This may bereadily accomplished by continuously feeding the carbon peliets P intothe furnace along with the metal chips, and one arrangement for this isillustrated in FIGS. 1, 2 and in greater. detail in FIG. 7. Thus, asupply of the pellets P is held in hopper 90 (FIGS. 1 and 2) from whichthey feed by gravity through a flexible duct 92 to a distributing nozzle94 mounted adjacent the surface 86 of conveyor 34. Nozzle 94 is formedof a short length of metal tubing abutting against the surface 86 of theconveyor and having a notch 96 cut at the downstream side to allow thepellets to feed into admixture with the chips on conveyor The rate offeed of the pellets can be adjusted as needed simply by changing thesize of notch 96.

The arrangement shown more particularly in FIG. 1 for eflectingreciprocation of the pusher 4% is so designed as to enable most of thecomponents to be placed out of the zone of high temperature existingdirectly above the furnace 36. This simplifies bearing design andlubrication problems, as well as making fewer obstructions to a hood andflue above the furnace for carrying off excess heat and fumes. To thisend, pusher head 44) is supported on a shaft 42 depending from acantilever arm 44 which, in turn, is supported on a reciprocated column100 disposed laterally of furnace 36. Column 18:? is supported forvertical reciprocation in a cylinder 102 carried by a pair of radialarms 104 secured at their inner ends to a vertically disposed axle lltl.The latter is journaled in bearings 110, at its upper and lower ends,respectively, directly below and concentric with the axis of furnace 36.Cylinder 192 is apertured at 112 to permit access to the reciprocatingcolumn 1% therewithin, and one end of a lever 114 is pivotally attachedat 116 to column tilt). The other end of lever 114 is.

The initial setting of the pusher 'head and the length of its stroke areso adjusted as to avoid contact of the head with the molten metal in thefurnace at the bottom of its stroke, while at the top of its stroke thepusher is preferably lifted slightly above the surface of the blanket tofacilitate even distribution of incoming chips across the blanket.

Means is also provided for angularly or rotatively moving the pusherassembly about its axis, and as shown in FIG. 2 this comprises a secondactuator 13!). Operating ram 132 of this actuator is connected tocylinder 192, while the opposite end is fastened to a stationary framemem ber 134. Both ends of the actuator are pivotally connected at theirrespective points so that extension and retraction of the operating ram132 causes pusher assembly 46 to swing about its axle 1%, as shown indotted lines in FIG. 2. In this manner pusher head 4% can be angularlydisplaced so that the paddles or blades contact the carbonaceous blanketB at different points in its surface. In the drawings and moreparticularly in FIG. 5, the pusher head 40 is shown as having fourpaddles or blades 136 which radiate outwardly from a hub 138. Each ofpaddles 136 is of generally sectorial configuration as viewed in plan,and is of a size such that rotations of shaft 42 through 45 effects anoverlap of the area covered by the under surface of the paddles, wherebythe entire surface of the furnace may be covered by the pusher insuccessive steps of angular adjustment.

In order that the pusher as can be reciprocated rapidly without causingdisruption of the blanket B to the extent that air is admitted to thesurface of the molten metal, while at the same time assuring eflectivepoking of the chips into the blanket, the under surface of paddles 136is made comparatively flat and the upper surface is sloped, as forexample by making it hipped or roof-shaped, as seen best in FIG. 3. Thisprovides good action in submerging the chips in the blanket, while thehipped upper surface of the paddles prevents accumulation thereon ofincoming chips or excessive dragout of the chips and associated carbonblanket during its upward stroke.

In general, it has been found desirable to operate the pusher at a speedof around five to fifteen cycles per minute. The angular rotations ofthepusher is not critical and may in some cases be omitted. Where it isemployed, completion of the movement of the blade through its completedisplacement and return may typically be on the order of once or twice aminute. This angular displacement maybe accomplished completely in oneor two strokes of the pusher, or it may be done.

more gradually in smaller increments over a greater number of verticalreciprocations. The amount of angular displacement need, of course, beno more than that necessary to bring the paddles into contact with allportions of the blanket surface. Where there are four paddles as shownin the drawings, each of which has an angular width of 45, displacementof 45 will effect the foregoing result. A different number of paddles ordifferent widths will of course require correspondingly differentamounts of angular movement to cover the entire surface.

The action of the pusher head on the chips and carbonaceous blanket inthe furnace may be described somewhat as follows: When the pusher headis given its downward stroke to bring it into contact with andsubmersion in blanket B, substantially three things take place. First,much of the portion of blanket B immediately below each paddle blade136, together with the entrained chips in this portion, is depressed bythe fiat undersurfaces of the blades, causing a surge of molten metal toflow off through overflow spout 50 of the furnace. Simultaneously, thebody of molten metal in the furnace directly below each pusher bladetends to penetrate into the adjacent portion of the blanket and therebyto wet and assimilate the heated and entrained chips in that portion.And thirdly, the portion of the blanket in the free areas between blades136 rises about the blades. Due to the fluidity of the blanket and thespeed of pusher all, this last mentioned portion of blanket B goesthrough a churning ebullient action aiding in the complete envelopmentand comrningling of the chips deposited just previously in these areas,thus effecting a better rate of heat transfer between the blanket andthe chips.

The furnace 36 employed for melting the chips is of standardlow-frequency electric induction heating type having a crucible 37 inthe lower portion of which is formed :a loop or channel 14% passingaround one leg of a magnetic core 142. Molten metal in this loop acts asthe secondary of a transformer, the primary of which is provided by aninduction coil 144 mounted on a leg of the core within the lower portionof the furnace, all in well known manner. Ducts 14d and a housing 148provided on the underside of the furnace direct cooling air to the core.Electrical energy supplied to coil 144 produces high induced currents inthe molten metal in loop 146, thereby keeping it molten and serving tocause it to circulate through the channel, whereby a substan tiallyuniform temperature gradient in the molten mass of metal is maintainedthroughout the furnace.

Supply of current to coil 1% is controlled by proportioning device 78 inresponse to the temperature indication received from thermocouple 15%positioned within the thermocouple tube 63. This tube is made of specialalloy steel to withstand the high temperature in the turnace, andcooling air is forced through the upper portion of the tubing byintroduction at lateral 153. This cooling air is allowed simply toexhaust out of the upper end of tubing 68 around the thermocouple leads151 which are brought out at that point and run to control device 7i).

The melting furnace is also provided with an underpour spout 50, aspreviously mentioned, designed to maintain a constant level of themolten metal in the furnace. Spout is formed of special high temperatureresistant alloy steel similar to that used in thermocouple ducting 68.The lower end of pour spout 50 is disposed below the surface of themolten metal to avoid inclusion of portions of the carbonaceous blanketor more importantly of any particles of unmelted, undissolved iron, aspreviously mentioned. Molten metal normally passes out through theoverflow arm of the spout as the level in the crucible tends to risewith melting of chips as they are added to the furnace. The overflowmetal passes through leg 152 of the spout into a heated launder 52 andthen into the hold furnace 54. As shown in FlGS. l and 3, spout 50 isalso provided with a clean-out extension 154 through which a curvedpusher may be run in case of a tendency of the metal to congeal andblock the overflow.

Hold furnace 54- is an induction furnace essentially similar to meltingfurnace 36 but is mounted for tilting movement to enable metal to bepoured ofi, whereas the melt furnace 36 does not tilt. This tiltingarrangement is desirable and conventional with pouring furnaces sincethe rate at which molten metal is poured into a billet mold is importantin producing a billet of uniform, dense sec tion throughout its length.Since the desired rate of pouring into a mold is generally differentfrom the rate of melting the chips in furnace as, bold furnace 5% actsas a temporary reservoir or accumulator until sufficient molten metal isavailable to pour a full billet :at a constant predetermined rate ofpour. At such time, the pour furnace is tilted by actuation of operatingram res of hydraulic or pneumatic cylinder 158 (see FIG. 4).

As in the melt furnace, it is likewise desirable in the pour furnace tomaintain an overlying blanket B of carbonaceous material to preventformation of excess dross on the surface of the melt. In this case theblanket need not be as thick as in the chip melting furnace, and usulalythree or four inches is ample. A dam led adjacent the pour spout may beused to retain the blanket on the sur face of the melt while the furnaceis tipped to pour metal into a mold.

The pour furnace may also be employed to melt heavier scrap stock in theform of chunks or the like which can be introduced automatically ormanually. In this respect, the hold furnace is used in the presentlyconventional manner of melting scrap where, because of the greaterWeight of this type of scrap, getting the scrap quickly into the mass ofmolten metal before substantial oxidation occurs presents no significantproblem. Thus double use of the hold furnace, i.e., for accumulatingmolten metal from the chip melting furnace and simultaneously meltingheavier scrap, provides an integrated system capable of accepting alltypes of scrap.

From the pour furnace, the molten metal passes through a strainer 60into the billet molds 62 (FIG. 1), as previously described, where it isallowed to cool. After the billet is cooled, the mold, which is of thesplit type and hinged along one side, is opened to expose the billetwhich can then be lifted by hoist 63 and placed on a. lowering conveyor64 for deposit on skids 66.

The temperature normally to be maintained both in the melt furnace 36and pour furnace 54 is one which is sufficiently high to maintain themetal in quite fluid condition but which, in the case of brass, is notso high as to cause excessive volatilization of the zinc content. Intypical chip brass, the melting temperature is on the order of 1630 to1650 F Zinc begins to boil at around 1950 F. Furnace temperaturesbetween these limits are suitable but improved performance and increasedrate of production are obtained as the average temperature in the meltis raised to something approaching the high limit.

Various modifications in the specific apparatus herein described forillustration purposes are of course possible without departing from theinventive concept, and all such modifications as fall within the scopeof the appended claims are accordingly intended to be included.

What is claimed is:

1. Apparatus for melting loose brass chip scrap which comprises acrucible furnace for holding a body of molten brass and a coveringblanket of finely divided fluent carbonaceous material, conveyor meansfor transporting said chip scrap to said furnace and for distributing itacross the surface of said carbonaceous blanket, a mechanical pusherdisposed above the level of molten metal in said furnace and adapted andarranged to be brought into contact with said carbonaceous blanket andthe loose chip scrap deposited thereon for promoting submergence of thechip scrap in said blanket, said pusher comprising a paddle having asubstantially broad flat undersurface and a sloping upper surface,support means for said paddle comprising a column positioned laterallyof said furnace and an arm on said column from which said paddle issuspended, and reciprocating means located below the top of the furnacefor supporting said column and reciprocating it axially to produceagitation of said carbonaceous blanket by said paddle.

2. Apparatus as defined in claim 1, wherein said reciprocating means forsaid pusher is mounted beneath said furnace and said column is supportedthereby for swinging movement in a horizontal plane about an axissubstantially concentric with the axis of said furnace.

3. Apparatus as defined in claim 2, wherein said pusher is provided witha plurality of paddles disposed radially, the outer ends of which extendclosely adjacent the side of the crucible, and wherein said pusher isrotated relative to the furnace in successive increments whereby reciprocation of the paddles may be effected throughout the entire surface ofthe crucible.

4. Apparatus as defined in claim 1, wherein said conveyor means fortransporting said chip scrap to said furnace includes a substantiallyhorizontal surface and means for vibrating said surface to impartforward motion to the chip scrap carried thereby, and a hopper for asupply of said finely divided carbonaceous material constituting saidblanket, said hopper having an open-ended duct ter- 11 minating in fixedposition closely adjacent the surface of said conveyor whereby vibrationof said conveyor surface relative to said duct controls the rate of feedof said carbonaceous material on to said surface. 1

5. Apparatus for melting loose brass chip scrap which comprises acrucible furnace adapted to hold a body of molten brass and a coveringblanket of finely divided fluent carbonaceous material, conveyor meansfor transporting said chip scrap to said furnace and for distributing itacross the surface of said carbonaceous blanket, pusher means adaptedand arranged for vertical reciprocation into and out of saidcarbonaceous blanket above said molten metal, and means disposed belowsaid furnace for reciprocating .said pusher; variable speed drive meansfor said conveyor for controlling the rate of delivery of said chipscrap to said furnace, and temperature means responsive to thetemperature of the molten brass in said furnace, said temperature meanscomprising a thermocouple element responsive to the temperature of themelt in the furnace and a protective tube for said thermocouple, saidtube having a leg closed at its lower end and extending into the moltenmetal in the furnace, said thermocouple element being disposed in saidtube adjacent said closed end, said tube being open at its upperrend andbeing provided intermediate its ends with a lateral, and a source ofcooling air connected to said tube and including means for passing saidair through said open end and said lateral above said thermocoupleelement.

6. Apparatus for melting loose brass chip scrap, which comprises afurnace having an open-faced crucible for holding a body of moltenmetal, conveyor means for transporting the chip scrap to said furnace,said conveyor having a forward extension partially overlying saidfurnace and being contoured at its outer free end to effect distributionof chip scrap across the open face of the crucible, a mechanical pusherdisposed in the open face of said crucible below said conveyor extensionand adapted and arranged to be brought into contact with accumulatedchip scrap deposited in said crucible, said pusher comprising apaddle-like member having a substantially broad fiat undersurfaceconstituting a significant portion of the open face area of saidcrucible but less than the total area thereof to allow chip scrap topass around said paddle-like member in entering the crucible, saidpaddle-like member having a sloping upper surface whereby to facilitatesuch passage, support means for said paddle positioned laterally of thefurnace and including an arm projecting over said crucible from whichsaid paddle-like member is suspended, and reciprocating means locatedbelow the top of the furnace to which said paddle support means issecured and by which it is reciprocated axially of said crucible tocontact accumulated chip scrap and effect agitati-on and envelopmentthereof by the body of molten metal. 3

References Cited by the Exer UNITED STATES PATENTS Re. 25,034 8/61Proler 75 43x 1,630,361 5/27 Stay etal. 266 33 1,659,445 2/28 Schmeller26633 2,232,594 2/41 Dike. 2,343,337 3/44 Somes 266--33 X 2,402,498 6/46Kohlhepp 26633 2,446,637 8/48 Champton ell a1 7565 2,493,391 1/50 Chew75 2,739,800 3/56 Sisco 26627 2,793,852 5/57 Harrison -65 2,868,396 1/59Helbing 214 1s.2 3,123,466 3/64 Crampton 75--65 FOREIGN PATENTS 685,8727/30 France.

OTHER REFERENCES Iron Age, June 4, 1942, pages 54-58. Copy in ScientificLibrary, 75-65.

JOHN F. CAMPBELL, Primary Examiner. RAY K. WINDHAM, MORRIS o. WOLK,Examiners.

1. APPARATUS FOR MELTING LOOSE BRASS CHIP SCRAP WHICH COMPRISES ACRUCIBLE FURNACE FOR HOLDING A BODY OF MOLTEN BRASS AND A COVERINGBLANKET OF FINELY DIVIDED FLUENT CARBONACEOUS MATERIAL, CONVEYER MEANSFOR TRANSPORTING SAID CHIP SCRAPO TO SAID FURNACE AND FOR DISTRIBUTINGIT ACROSS THE SURFACE OF SAID CARBONACEOUS BLANKET, A MECHANICAL PUSHERDISPOSED ABOVE THE LEVEL OF MOLTEN METAL IN SAID FURNACE AND ADAPTED ANDARRANGED TO BE BROUGHT INTO CONTACT WITH SAID CARBONACEOUS BLANKET ANDTHE LOOSE CHIP SCRAP DEPOSITED THEREON FOR PROMOTING SUBMERGENCE OF THECHIP SCRAP IN SAID BLANKET, SAID PUSHER COMPRISING A PADDLE HAVING ASUBSTANTIALLY BROAD FLAT UNDERSURFACE AND A SLOPING UPPER SURFACE,SUPPORT MEANS FOR SAID PADDLE COMPRISING A COLUMN POSITIONED LATERALLYOF SAID FURNACE AND AN ARM ON SAID COLUMN FROM WHICH SAID PADDLE ISSUSPENDED, AND RECIPROCATING MEANS LOCATED BELOW THE TOP OF THE FURNACEFOR SUPPORTING SAID COLUMN AND RECIPROCATING IT AXIALLY TO PRODUCEAGITATION OF SAID CARBONACEOUS BLANKET BY SAID PADDLE.